Contao\Image::setImportantPart PHP Method

    public function setImportantPart(array $importantPart = null)
    {
        if ($importantPart !== null) {
            if (!isset($importantPart['x']) || !isset($importantPart['y']) || !isset($importantPart['width']) || !isset($importantPart['height'])) {
                throw new \InvalidArgumentException('Malformed array for setting the important part!');
            }
            $this->importantPart = array('x' => max(0, min($this->fileObj->viewWidth - 1, (int) $importantPart['x'])), 'y' => max(0, min($this->fileObj->viewHeight - 1, (int) $importantPart['y'])));
            $this->importantPart['width'] = max(1, min($this->fileObj->viewWidth - $this->importantPart['x'], (int) $importantPart['width']));
            $this->importantPart['height'] = max(1, min($this->fileObj->viewHeight - $this->importantPart['y'], (int) $importantPart['height']));
        } else {
            $this->importantPart = null;
        }
        return $this;
    }

 /**
  * {@inheritdoc}
  */
 public function resize(ImageInterface $image, ResizeConfigurationInterface $config, ResizeOptionsInterface $options)
 {
     if (!empty($GLOBALS['TL_HOOKS']['executeResize']) && is_array($GLOBALS['TL_HOOKS']['executeResize']) || !empty($GLOBALS['TL_HOOKS']['getImage']) && is_array($GLOBALS['TL_HOOKS']['getImage'])) {
         @trigger_error('Using the executeResize and getImage hooks has been deprecated and will no longer work in Contao 5.0. Replace the contao.image.resizer service instead.', E_USER_DEPRECATED);
         $this->legacyImage = null;
         $legacyPath = $image->getPath();
         if (0 === strpos($legacyPath, TL_ROOT . '/') || 0 === strpos($legacyPath, TL_ROOT . '\\')) {
             $legacyPath = substr($legacyPath, strlen(TL_ROOT) + 1);
             $this->legacyImage = new LegacyImage(new File($legacyPath));
             $this->legacyImage->setTargetWidth($config->getWidth());
             $this->legacyImage->setTargetHeight($config->getHeight());
             $this->legacyImage->setResizeMode($config->getMode());
             $this->legacyImage->setZoomLevel($config->getZoomLevel());
             if ($options->getTargetPath() && (0 === strpos($options->getTargetPath(), TL_ROOT . '/') || 0 === strpos($options->getTargetPath(), TL_ROOT . '\\'))) {
                 $this->legacyImage->setTargetPath(substr($options->getTargetPath(), strlen(TL_ROOT) + 1));
             }
             $importantPart = $image->getImportantPart();
             $this->legacyImage->setImportantPart(['x' => $importantPart->getPosition()->getX(), 'y' => $importantPart->getPosition()->getY(), 'width' => $importantPart->getSize()->getWidth(), 'height' => $importantPart->getSize()->getHeight()]);
         }
     }
     if (isset($GLOBALS['TL_HOOKS']['executeResize']) && is_array($GLOBALS['TL_HOOKS']['executeResize']) && $this->legacyImage) {
         foreach ($GLOBALS['TL_HOOKS']['executeResize'] as $callback) {
             $return = System::importStatic($callback[0])->{$callback[1]}($this->legacyImage);
             if (is_string($return)) {
                 return $this->createImage($image, TL_ROOT . '/' . $return);
             }
         }
     }
     return parent::resize($image, $config, $options);
 }